1. Field of the Invention
The present invention relates to a bypass turbo-jet engine thrust reverser having a scoop-type door and at least one movable cascade.
2. Description of the Related Art
At the rear of a fan designed to channel the so-called cold, bypass flow, a turbojet engine is fitted with a duct 17 consisting of an inner wall enclosing the actual engine structure and an outer wall which is continuous with the engine cowling enclosing the fan. This outer wall is able to simultaneously channel the bypass flow and the primary flow to the rear of the exhaust of the so-called hot, primary flow as regards a mixed- or confluent-flow, but in other cases the outer wall may only channel the bypass flow as regards a separate flow.
Moreover, a wall may fair the outside of the casing enclosing the outside of the outer wall of the above described duct, namely for the purpose of minimizing powerplant drag. This is especially the case for powerplants which project from the aircraft, in particular when such powerplants are mounted under the wings or at the rear of the fuselage.
European patent document EP 0,822,327 A discloses an illustrative embodiment, shown in FIG. 1 of the attached drawings, of a scoop-door thrust-reverser used in a bypass turbojet engine.
The thrust reverser consists of a movable sub-assembly and a stationary structure. The movable sub-assembly consists of a hollow door 3 forming a movable portion 2 and constituting, when in the forward-thrust mode, part of the external cowling. The stationary structure consists of an upstream portion 6 upstream of the door 3, a downstream portion 7 downstream of the door 3, and beams linking the upstream portion 6 to the downstream portion 7, the stationary structure also being part of the external cowling.
At least one door 3 is mounted along a circumference on the external cowling and is pivotable, in a downstream portion of its side walls, on the beams, situated on each side of the door, linking the downstream portion 7 to the upstream portion 6 of the external cowling. The side walls connect the external part, i.e., the outer panel 4 of the door 3, which constitutes a part of the external cowling, to an inner part 5 of the door 3, which constitutes a part of the outer wall of the duct.
The stationary-structure's upstream portion 6 comprises a forward frame 8 which may be used as a rest for a control means to displace the door 3, for instance linear actuators. This displacement control means for the door 3 may also be situated elsewhere on the periphery of the door 3, for instance downstream of it. In the latter case, the stationary structure's downstream portion 7 shall serve as the rest for the control means.
When driven toward an open position, the door 3 tips in such manner that the door portion upstream of a door pivot 9 more or less completely obstructs the duct 17 while clearing a passage in the external cowling to allow flows 13 and 14 to be channeled in a centrifugal direction relative to the duct axis, on one hand into an inner duct or conduit 10 constituted by the structure of the door 3, and on the other hand between a deflecting edge of the stationary structure and the outer panel 4 of the door 3. The door's downstream part is thereby moved into the vicinity of the outside of the external cowling. The door's pivot angle is adjusted in such manner so as to allow exhausting of the flow so as to strongly reduce, even suppress, the forward thrust of the flow, and to generate a counter-thrust by generating an upstream-directed flow component 13b.
The outer panel 4 of the door 3 of the above described thrust reverser model comprises an exhaust path for flow 14 between the deflection edge and the outer surface of the panel 14. The flow 14 meets the flow 13b exhausting from the door's inner duct 10. By merging with this flow 13b, the flow 14 minimizes the forward direction assumed by the flow 13b.
French patent application 97.06943 solves this problem by using a movable baffle 5 positioned above the outer panel of the door 3 when the door opens so as to limit, or restrict any interference between the door's exhaust flow and the flow deflected by the door's outer panel. FIG. 2 shows an embodiment of this invention in the thrust-reversal position.
For reasons of seating and kinematics, the sort of baffle 5 described in French patent application 97.06943 will partly or totally cover the cascade vanes in the forward-thrust mode. During opening, at least the downstream part of the baffle starts from a blade-straddling position 5a and moves toward a position 5b in which it covers the door's outer panel 4. During the thrust-reversal operation, an exhaust aperture 15 for the door's flow 13 cannot be completely freed and thus cannot allow free thrust-reversal flow transmission. Consequently, performance problems may arise in the turbojet engine because the cross-section of the annular duct 17 obstructed by the door 3 might not be compensated by the flow-transmitting cross-section freed by the door.
The forward-thrust positioning of the baffle does not allow, or only with great difficulty, the optimal shape, as desired by expert, of the baffle 5.
Unless carefully applied, a sealing means 12 between the downstream zone of the baffle 5 and the outer panel 4 may entail some performance degradation due to part of the flow moving above the outer panel 4 toward the flow exhausting from the door 3.
The baffle 5 is driven by a linkage system mounted outside the sides of the door 3 and secured to the door. The guidance technique using four linkrods entails a multiplicity of drive parts and requires rigorous manufacture to attain the reliability required of the thrust reverser.
Lastly, the configuration of the stationary vanes is designed to secure optimal thrust-reversal performance. It is impossible to direct the flow forward in the manner considered optimal by expert during opening of the door 3.